Method of controlling a device that varies the valve control times an internal combustion engine, especially of a camshaft adjusting device with hydraulically releaseable start lock

ABSTRACT

A method of actuating a device for varying the valve timing of an internal combustion engine without jamming of the locking element during starting of the internal combustion engine, the solenoid of the hydraulic valve is at first energized through a number of high frequency cycles of high and low energization that are broken off after a defined period of time or after a defined number of cycles, followed by a renewed energization of the solenoid with a high energization with a simultaneous check by the microprocessor to determine whether the element fixed to the camshaft has been angularly displaced relative to the element fixed to the crankshaft out of its basic position whereby if the microprocessor determines that the element fixed to the crankshaft is still in the basic position, the first two phases of energization are repeated and the microprocessor has determined an angular displacement of the element fixed to the camshaft, the solenoid is energized with a current defined by the microprocessor which is of a higher intensity than that required for the central position of the valve piston of the hydraulic valve.

FIELD OF THE INVENTION

The invention concerns a method of actuating a device for varying thevalve timing of an internal combustion engine, which method can beadvantageously implemented particularly in all types of camshaftadjusting devices having a hydraulically releasable start locking.

BACKGROUND OF THE INVENTION

Such a method relates particularly to camshaft adjusting devices of thegeneric type disclosed in DE-OS 197 26 300. These devices, generallydesignated in the technical field as axial piston and rotary pistonadjusting devices, are arranged, irrespective of their structure, on thedrive-side end of a camshaft mounted in the cylinder head of theinternal combustion engine while being generally configured as hydraulicadjusting drives that comprise an element fixed in driving relationshipto the crankshaft of the internal combustion engine and an elementrotationally fixed to the camshaft. The element fixed to the crankshaftis in power-transmitting relationship with the element fixed to thecamshaft through at least one hydraulic working chamber configuredwithin the device, each hydraulic working chamber being divided by anadjusting element within the device into a so-called. A pressure chamberand a B pressure chamber. A pivoting or fixing of the element fixed tothe camshaft relative to the element fixed to the crankshaft is effectedby a selective or a simultaneous pressurizing of the A and/or B pressurechamber of each hydraulic working chamber, the pressurizing of thepressure chambers being controlled by an electromagnetically actuatedvalve piston of a hydraulic valve whose solenoid is actuated by amicroprocessor as a function of different operation parameters of theinternal combustion engine. Normally, this valve piston of the hydraulicvalve permits, in a non-energized or low energized state of thesolenoid, a pressurization of the B pressure chamber of each hydraulicworking chamber, in a high or maximum energized state of the solenoid, apressurization of the A pressure chamber of each hydraulic workingchamber, and in a central position, a holding of the pressure mediumpressure in both pressure chambers of each hydraulic working chamber ofthe device. When the internal combustion engine has been switched offand the volume of the A pressure chamber of each hydraulic workingchamber is minimized, the element fixed to the camshaft can bemechanically coupled to the element fixed to the crankshaft in apreferred basic position for starting the internal combustion engine,coupling be achieved by an additional locking element arranged on theelement fixed to the camshaft or on the element fixed to the crankshaft,which locking element can be displaced by a spring element into acoupling position within a complementary reception in the element fixedto the crankshaft or in the element fixed to the camshaft. Thiscomplementary reception of the locking element is hydraulicallyconnected to the pressure medium supply to the volume-minimized Apressure chamber of at least one hydraulic working chamber of thedevice, so that, upon pressurization of the volume-minimized A pressurechamber of each hydraulic working chamber during starting of theinternal combustion engine, the reception of the locking element islikewise pressurized and the locking element is displaced hydraulically,against the force of its spring element, into an uncoupling position.

This shock-like pressurization of the volume-minimized A pressurechamber generally effected by a short pulse on the solenoid at maximumenergization has proved to be a drawback in practice because the suddenrise of pressure in all the volume-minimized A pressure chambers causesa bracing moment to act on the locking element which leads to a jammingof the locking element in its coupling position particularly when themean moment of drag of the camshaft acts in the same direction as thebracing moment and/or when the time for building up the bracing momentis shorter than the time for displacing the locking element into itsuncoupling position. As a consequence, a relative rotation between theelement fixed to the camshaft and the element fixed to the crankshaftinto a defined angle given by the microprocessor is no longer possible,so that, for example, in the case of inlet-side camshaft adjustingdevices there are performance deficits of the internal combustionengine, and in the case of outlet-side camshaft adjusting devices, theinternal combustion engine has higher emission values.

OBJECT OF THE INVENTION

The object of the invention is therefore to provide a method ofactuating a device for varying the valve timing of an internalcombustion engine, particularly a camshaft adjusting device having ahydraulically releasable start locking, which method enables a reliableprevention of a jamming of the locking element in its coupling positioneven when a bracing moment resulting from a pressurization and a meanmoment of drag of the camshaft impede movement of the locking element inthe same direction.

SUMMARY OF THE INVENTION

The invention achieves this object in a camshaft adjusting device havinga hydraulically releasable start locking, said device generallycomprising following features:

the device (1) is arranged on the drive-side end of a camshaft (3)mounted in the cylinder head of the internal combustion engine andgenerally configured as a hydraulic adjusting drive,

said device (1) comprising an element (4) fixed in driving relationshipto a crankshaft of the internal combustion engine and an element (5)rotationally fixed to the camshaft (3),

the element (4) fixed to the crankshaft is in powder-transmittingrelationship with the element (5) fixed to the camshaft through at leastone hydraulic working chamber (6) formed within the device (1),

each hydraulic working chamber (6) of the device (1) is divided by anadjusting element (7) within the device (1) into a pressure chamber (8)and a pressure chamber (9),

a pivoting or fixing of the element (5) fixed to the camshaft relativeto the element (4) fixed to the crankshaft is effected by a selective ora simultaneous pressurizing of the pressure chamber (8, 9) of eachhydraulic working chamber (6),

the pressurizing of pressure chamber (8, 9) of each hydraulic workingchamber (6) is regulated by an electromagnetically actuated valve pistonof a hydraulic valve (10) whose solenoid (11) is actuated by a microprocessor (12) as a function of different operation parameters of theinternal combustion engine,

the valve piston of the hydraulic valve (10) permits, in a non-energizedor low energized state of the solenoid (11), a pressurization of thepressure chamber (9), in a high or maximum energized state of thesolenoid (11), a pressurization of the pressure chamber (8), and in acentral position, a holding of the pressure medium pressure (P) in bothpressure chambers (8, 9) of each hydraulic working chamber (6) of thedevice (1),

when the internal combustion engine has been switched off and the volumeof the pressure chamber (8) of each hydraulic working chamber (6) hasbeen minimized, the element (5) fixed to the camshaft can bemechanically coupled to the element (4) fixed to the crankshaft in apreferred basic position for starting the internal combustion engine,

the mechanical coupling is achieved by a locking element (13) arrangedon the element (5) fixed to the camshaft or on the element (4) fixed tothe crankshaft, which locking element (13) can be displaced by a springelement (14) into a coupling position within a complementary reception(15) in the element (4) fixed to the crankshaft or in the element (5)fixed to the camshaft,

the complementary reception (15) of the locking element (13) ishydraulically connected to the pressure medium supply (16) tovolume-minimized pressure chamber (8) of at least one hydraulic workingchamber (6) of the device (1),

upon pressurization of the volume-minimized pressure chamber (8) of eachhydraulic working chamber (6) during starting of the internal combustionengine, the reception (15) of the locking element (13) is likewisepressurized and the locking element (13) is displaced hydraulically,against the force of its spring element (14), into an uncouplingposition, by the fact that the solenoid of the hydraulic valve (10)operated on starting of the internal combustion engine following aregulation strategy comprising the steps

(a) energization for a defined period of time (t), through a number ofhigh frequency cycles of high and low energization (1), or through adefined number of such cycles, so that the valve piston of the hydraulicvalve (10) oscillates in a range about its central position and enablesa rapid alternating pressurization of the pressure chambers (8, 9) ofeach hydraulic working chamber (6) of the device (1) with a pressure (P)with which the element (5) fixed to the camshaft is held in its basicposition,

(b) at the end of the defined period of time (t) or the last cycle, theroutine is broken off and followed by a renewed energization or aholding of the high energization (1) for a further defined period oftime (t) in which the microprocessor (12) simultaneously checks whetherthe element (5) fixed to the camshaft has been angularly displacedrelative to the element (4) fixed to the crankshaft out of itsbasic-position and the locking element (13) has therefore taken itsuncoupling position,

(c) if the microprocessor (12) determines that the element (5) fixed tothe camshaft is still in its basic position, steps (a) and (b) rerepeated till the microprocessor (12) registers that the element (5)fixed to the camshaft has been angularly displaced relative to theelement (4) fixed to the crankshaft out of its basic position and thatthe locking element (13) has therefore taken its uncoupling position,

(d) when the microprocessor (12) determines an angular displacement ofthe element (5) fixed to the camshaft out of its basic position,energization with a current (1) defined by the Microprocessor (12) whichis of a higher intensity than that required for the central position ofthe valve piston of the hydraulic valve (10) and corresponds to anadjusted angular position of the element (5) fixed to the camshaftrelative to the element (4) fixed to the crankshaft.

Alternatively, the invention also achieves this object in the device bythe fact that the solenoid of the hydraulic valve is operated onstarting of the internal combustion engine following a regulationstrategy comprising the steps:

a) energization with a high current (1) in a defined period of time (t),so that, at first, only the volume-minimized pressure chamber (8) ofeach hydraulic pressure chamber (6) of the device (1) and, thus also,the reception (15) of the locking element (13) is pressurized with ahigh pressure medium pressure (P_(A)),

b) at the end of the defined period of time (t), the Microprocessor (12)checks whether the element (5) fixed to the camshaft has been angularlydisplaced relative to the element (4) fixed to the crankshaft out of itsbasic position and that the locking element (13) has therefore taken itsuncoupling position,

c) if the microprocessor (12) determines that the element (5) fixed tothe camshaft is still in its basic position, the solenoid (11) isenergized with a low current (1) for a further period of time (t) for abrief pressurization of the pressure chamber (9) of each hydraulicworking chamber (6) with a pressure medium pressure (P_(B)) followed bya repetition of steps a) and b) till the microprocessor (12) registersthat the element (5) fixed to the camshaft has been angularly displacedrelative to the element (4) fixed to the crankshaft out of its basicposition and that the locking element (13) has therefore taken itsuncoupling position,

d) after determination of an angular displacement of the element (5)fixed to the camshaft out of its basic position, energization with acurrent (1) defined by the microprocessor (12) which is of a higherintensity than that required for the central position of the valvepiston of the hydraulic valve (10) and corresponds to an adjustedangular position of the element (5) fixed to the camshaft relative tothe element (4) fixed to the crankshaft.

According to the first embodiment of the method of the invention, aso-called high frequency pulsed start of the device is effected in thatthe solenoid of the hydraulic valve is at first energized for a definedperiod of time through a number of high frequency cycles of high and lowenergization, or through a defined number of such cycles, so that thevalve piston of the hydraulic valve oscillates in a range about itscentral position and thus enables a rapid alternating pressurization ofthe A and the B pressure chambers of each hydraulic working chamber ofthe device with a pressure medium pressure with which the element fixedto the camshaft is held in its basic position. At the end of the definedperiod of time or the last cycle, the said routine is broken off andthis is followed by a renewed energization or a holding of the highenergization for a further defined period of time in which themicroprocessor simultaneously checks whether the element fixed to thecamshaft has been angularly displaced relative to the element fixed tothe crankshaft out of its basic position and the locking element hastherefore taken its uncoupling position. If the microprocessordetermines that the element fixed to the camshaft is still in its basicposition, the cycles of high and low energization are repeated for thesame defined period of time, or number of cycles, followed by a renewedenergization or holding of the high energization till the microprocessorregisters that the element fixed to the camshaft has been angularlydisplaced relative to the element fixed to the crankshaft out of itsbasic position and that the locking element has therefore taken itsuncoupling position. When the microprocessor determines an angulardisplacement of the element fixed to the camshaft out of its basicposition, the solenoid is energized with a current defined by themicroprocessor which is of a higher intensity than that required for thecentral position of the valve piston of the hydraulic valve andcorresponds to an adjusted angular position of the element fixed to thecamshaft relative to the element fixed to the crankshaft.

According to an advantageous feature of this first embodiment of themethod of the invention, it is further proposed to control the high andthe low energization of the solenoid of the hydraulic valve preferablyby a pulse width modulated voltage control of the microprocessor, sothat the energization of the solenoid within one high frequency cycle iseffected, once, with an electric current having an intensity between 5%above that required for the central position of the valve piston of thehydraulic valve and 95% of the maximum intensity, and, once, with anelectric current having an intensity of between 5% of the maximumintensity and an intensity that is 5% lower than that required for thecentral position of the valve piston of the hydraulic valve. However, inplace of a pulse width modulated voltage control with this setting, itis also possible to realize this with a current regulation of a knowntype. Within the limits of the above-defined control ranges, the shareof high and low energization of the solenoid can be freely chosen inboth cases to be symmetric or asymmetric and the form of the transitionfrom high to low energization, and vice versa, to be sudden or gradual,or the like. The respective lower limits of the pulsation ranges of thevalve piston of 5% above and 5% below the energization required for thecentral position have proved to be of advantage because they reliablyprevent a sinking of the volume flow of the hydraulic pressure medium tothe A and the B pressure chamber of each hydraulic working chamber belowa value at which the basic position of the element fixed to the camshaftcan no longer be maintained.

As a further feature of the first embodiment of the method of theinvention, it is finally proposed that, if the criterion for breakingoff the routine consisting of the high frequency cycles is defined interms of time, the duration of a cycle is preferably between 4 ms and 10ms and the period of time for all the cycles required to displace thelocking element into its uncoupling position till the breaking off ofthe routine is limited to a range of 10 ms to 40 ms. If, in contrast,the criterion for breaking off is defined in numbers, advantageously,the number of high frequency cycles required to displace the lockingelement into its uncoupling position till the breaking off of theroutine is limited to 2 to 8 repetitions. It has been shown in practice,that in most cases, already one routine limited in time or in number tothe ranges defined above is sufficient for reliably displacing thelocking element into its uncoupling position.

According to the second embodiment of the method of the invention, incontrast, a so-called low frequency pulsed start of the device iseffected in that the solenoid of the hydraulic valve is at firstenergized with a high current in a defined period of time, so that onlythe volume-minimized A pressure chamber of each hydraulic pressurechamber of the device and, thus also, the reception of the lockingelement is pressurized with a high pressure medium pressure. At the endof this defined period of time, the microprocessor checks whether theelement fixed to the camshaft has been angularly displaced relative tothe element fixed to the crankshaft out of its basic position and thelocking element has therefore taken its uncoupling position. If themicroprocessor determines that the element fixed to the camshaft isstill in its basic position, the solenoid is energized with a lowcurrent for a further period of time for a brief pressurization of the Bpressure chamber of each hydraulic working chamber. This is followed bya renewed energization of the solenoid with a high current for a definedperiod of time till the microprocessor registers that the element fixedto the camshaft has been angularly displaced relative to the elementfixed to the crankshaft out of its basic position and that the lockingelement has therefore taken its uncoupling position. After determinationof an angular displacement of the element fixed to the camshaft out ofits basic position, the solenoid is finally energized, in thisembodiment, too, with a current defined by the microprocessor which isof a higher intensity than that required for the central position of thevalve piston of the hydraulic valve and corresponds to an adjustedangular position of the element fixed to the camshaft relative to theelement fixed to the crankshaft.

As an advantageous feature of this second embodiment of the method ofthe invention, too, it is proposed to control the energization of thesolenoid of the hydraulic valve preferably by a pulse width modulatedvoltage control of the microprocessor, so that the energization of thesolenoid with a high current is effected preferably between 90% and 100%of the maximum electric current, and the energization of the solenoidwith a low current is effected preferably between 0% and 10% of themaximum electric current. Similar to the first embodiment of the methodof the invention, this can also be alternatively achieved using acurrent regulation of a known type. Within the above-defined controlranges, the share of high and low energization of the solenoid can befreely chosen in both cases to be symmetric or asymmetric. The durationof high energization is preferably set between 40 ms an 80 ms while theduration of low energization is limited to a range of between 10 ms and40 ms. The purpose of this brief low energization of the solenoid andthe accompanying pressurization of the B pressure chamber of eachhydraulic working chamber is to bring the element fixed to the camshaftthat, due to the previous pressurization of the A pressure chamber ofeach hydraulic working chamber, has been rotated through an angle (up to1° crankshaft angle) corresponding to the operational play of movementof the locking element and that may be jamming the locking element, backinto a position in which the locking element can move freely for thenext releasing attempt.

Both embodiments of the method of the invention for actuating a devicefor varying the valve timing of an internal combustion engine,particularly a camshaft adjusting device having a hydraulicallyreleasable start locking thus permit, in contrast to prior art actuatingmethods for devices of a similar type, a reliable prevention of ajamming of the locking element in its coupling position during thestarting of the internal combustion engine even when a bracing momentresulting from the pressurization of the volume-minimized A pressurechamber of each hydraulic working chamber of the device and a meanmoment of drag of the camshaft impede movement of the locking element inthe same direction. The high and low frequency energization of thesolenoid of the hydraulic valve with a high and a low current and theaccompanying alternating pressurization of the A and the B pressurechamber of each hydraulic working chamber of the device causes a“jolting” movement of the locking element which guarantees a reliablemovement of the locking element into its uncoupling position and, thusalso, a reliable releasing of the start locking of the device. In thisway, already immediately after the starting of the internal combustionengine, relative rotations between the element fixed to the camshaft andthe element fixed to the crankshaft into defined angular positions givenby the microprocessor are possible, and negative consequences such asreduced performance or increased emission of the internal combustionengine are excluded.

BRIEF DESCRIPTION OF THE DRAWINGS

The method according to the invention will now be described more closelywith reference to examples of embodiment and the appended drawings.

FIG. 1 shows a cross-section taken along line B—B of FIG. 2 through acamshaft adjusting device mounted on a camshaft, with a schematicrepresentation of pressure medium control;

FIG. 2 is a top view of a camshaft adjusting device corresponding tosection A—A of FIG. 1;

FIG. 3 is a current-time diagram showing the flow of current in thesolenoid of the hydraulic valve, according to a first embodiment of themethod of the invention;

FIG. 4 is a pressure-time diagram showing the flow of pressure in the Aand the B pressure chambers of each hydraulic working chamber of thedevice, according to the first embodiment of the method of theinvention;

FIG. 5 is a current-time diagram showing the flow of current in thesolenoid of the hydraulic valve, according to a second embodiment of theinvention;

FIG. 6 is a pressure-time diagram showing the flow of pressure in the Aand the B pressure chambers of each hydraulic working chamber of thedevice, according to the first embodiment of the method of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 and 2 show a device 1 for varying the valve timing of aninternal combustion engine with reference to which the method of theinvention will be described by way of example. The device 1 belongs tothe so-called rotary piston devices and is designated as a vane-typeadjuster. This device 1, as also the so-called axial piston devices, isgenerally configured as a hydraulic adjusting drive and is arranged onthe drive-side end of a camshaft 3 mounted in the cylinder head 2 of theinternal combustion engine. The device 1 comprises, in a known manner,an element 4 fixed to the crankshaft of the internal combustion enginein driving relationship with the crankshaft, and an element 5rotationally fixed to the camshaft 3, said elements 4, 5 being inpower-transmitting relationship through at least one hydraulic workingchamber 6 formed within the device 1. As can be seen in FIGS. 1 and 2,the element 4 fixed to the crankshaft is formed by a drive pinion 17configured as an outer rotor which comprises a hollow space 21 definedby a hollow cylindrical circumferential wall 18 and two side walls 19,20. In the present example, five hydraulic working chambers 6 are formedin the hollow space 21 by five limiting walls 22 extending from thecircumferential wall 18 towards the central longitudinal axis of thedevice 1. The element 5 fixed to the camshaft is formed by a rotor 23that is inserted into the hollow space 21 of the drive pinion 17 andcomprises five vanes 25 arranged on its hub 24, each vane 25 extendingradially into one of the hydraulic working chambers 6. The vanes of thisrotor 23, that is configured as an adjusting element 7 within the device1, divide each hydraulic working chamber 6 of the device 1 into an Apressure chamber and a B pressure chamber, which chambers, upon aselective or a simultaneous pressurization by a hydraulic pressuremedium effect a pivoting or a fixing of the rotor 23 relative to thedrive pinion 17 and, thus, of the camshaft 3 relative to the crankshaftof the internal combustion engine. The pressurization of the A and/or Bpressure chamber of each hydraulic working chamber 6 is regulated by theelectromagnetically actuated valve piston of a hydraulic valve 10,schematically represented in FIG. 1, whose solenoid 11 is actuated as afunction of different operation parameters of the internal combustionengine by a microprocessor 12, also represented only schematically inFIG. 1. The hydraulic valve 10, configured as a 4/3 directional controlvalve, is connected to a pressure medium pump 26 and a pressure mediumreservoir 27 and enables, in the position of its valve piston shown inFIG. 1 which corresponds to a non-energized or low energized solenoid11, a pressurization of the B pressure chamber 9, in the position of itsvalve piston: corresponding to a high or maximum energized solenoid. 11,a pressurization of the A pressure chamber 8, and in a central positionof its valve piston, a holding of the pressure medium pressure in bothpressure chambers 8, 9 of each hydraulic working chamber 6 of the device1.

A further feature of the device 1 shown in FIGS. 1 and 2 is that, afterthe internal combustion engine has been switched off, accompanied by avolume minimization of the A pressure chambers 8 of the hydraulicworking chambers 6, the element 5 fixed to the camshaft and configuredas a rotor 23 can be coupled mechanically to the element 4 fixed to thecrankshaft and configured as a drive pinion 17 in a preferred basicposition for starting the internal combustion engine. Depending onwhether the device 1 is mounted on an in let or an outlet camshaft, thisbasic position corresponds to a “retard” or an “advance” position of thecamshaft 3 relative to the crankshaft which is reached when the vanes 25of the rotor 23 come into an end position on one or the other of thelimiting walls 22 of each hydraulic working chamber 6. FIG. 2 shows adevice 1 connected to an outlet camshaft with the rotor 23 rotatedalmost into the basic i.e., “advance” position. As best seen in FIG. 1,the mechanical coupling is effected by a pin-like locking element 13arranged for displacement in an axial bore, not referenced, in the hub24 of the rotor 23. This locking element 13 can be displaced by a springelement 14 into a coupling position within a complementary reception 15in the side wall 19 of the drive pinion 17. FIG. 2 further shows thatthe complementary reception 15 of the locking element 13 is arrangedwithin the pressure medium supply 16 to a volume-minimized A pressurechamber 8 of a hydraulic working chamber 6 of the device 1, so that,when the internal combustion engine is started, the pressurization ofthe A pressure chambers of the hydraulic working chambers 6 results in asimultaneous pressurization of the reception 15 of the locking element13 which is then displaced hydraulically, against the force of itsspring element 14, into its uncoupling position in the axial bore in thehub 24 of the rotor 23.

To avoid a bracing moment acting on the locking element 13 due to asudden pressurization of the volume-minimized A pressure chambers 8 onstarting of the internal combustion engine, which bracing momenttogether with a mean moment of drag of the camshaft 3 also acting in thesame direction, causes a jamming of the locking element 13 in itscoupling position, the solenoid 11 of the hydraulic valve 10 is operatedaccording to a first regulation strategy, provided by the invention andgraphically represented in diagrams in FIGS. 3 and 4, to assure ajam-free movement of the locking element 13 into its uncouplingposition. These diagrams show that on starting of the internalcombustion engine, the solenoid 11 of hydraulic valve 10 is at firstenergized in a number of high frequency cycles of low and highenergization 1, so that the valve piston of the hydraulic valve 10oscillates in a range about its central position. This enables a rapidalternating pressurization of the A and the B pressure chambers 8, 9 ofthe hydraulic working chambers 6 of the device 1 with a pressure P_(A)and P_(B), represented in FIG. 4 as a broken and a solid line,respectively, with which the rotor 23 is held hydraulically in its basicposition. Each high frequency cycle lasts for 4 ms to 10 ms and the timeperiod t for all the cycles is limited to a range of 10 ms to 40 ms, orthe total number of cycles is limited to 2 to 8 repetitions. During eachcycle, the energization of the solenoid 11 is effected, once, with anelectric current I having an intensity of between 5% above that requiredfor the central position of the valve piston of the hydraulic valve 10and 95% of the maximum intensity, and, once, with an electric current Ihaving an intensity of between 5% of the maximum intensity and 5% belowthat required for the central position of the valve piston of thehydraulic valve 10. After the lapse of the time limit of 40 ms or also,as shown in the example represented in FIGS. 3 and 4, at the end of 5cycles, this routine is broken off. This is followed by a renewedenergization of the solenoid 11 for a further period of 4 ms to 10 mswith a current I having an intensity of between 5% above that requiredfor the central position of the valve piston of the hydraulic valve 10and 95% of the maximum intensity and a simultaneous check by themicroprocessor 12 whether the rotor 23 has been angularly displacedrelative to the drive pinion 17 out of its basic position and thelocking element 13 has therefore taken its uncoupling position. If themicroprocessor 12 determines that the rotor 23 is still in its basicposition, the cycles are repeated with the same current intensity in thesame number or time period till the microprocessor 12 registers that therotor 23 has been angularly displaced relative to the drive pinion 17out of its basic position and that the locking element 13 has thereforetaken its uncoupling position. When such an angular displacement of therotor 23 out of its basic position has been determined by themicroprocessor 12, which can be the case after a number of routines havebeen performed, or as represented in FIGS. 3 and 4, already afterperformance of the first routine, the routine is likewise broken off andthe solenoid 11 of the hydraulic valve 10 is immediately subjected to acurrent I that is defined by the microprocessor 12 and corresponds to anadjusted angular position of the rotor 23 relative to the drive pinion17. This current has an intensity situated in a range above thatrequired for the central position of the valve piston of the hydraulicvalve 10 up to 100% of the maximum intensity.

A further possibility to avoid a bracing moment acting on the lockingelement 13 and, thus, a jamming the locking element 13 in its couplingposition, is shown in the diagrams of FIGS. 5 and 6. According to thesediagrams, the solenoid 11 of the hydraulic valve 10 is operatedfollowing a second regulation strategy of the invention in that thesolenoid 11 is at first energized in a time period t of 40 ms to 80 mswith a current I between 90% and 100% of the maximum intensity, so thatto begin with, again, only the volume-minimized A pressure chambers 8 ofthe hydraulic working chambers 6 of the device 1 and, thus also, thereception 15 of the locking element 13 are pressurized with a highpressure medium pressure P_(A) corresponding to the broken-line pressurecurve in FIG. 6. After the lapse of the time period of 40 ms to 80 ms,the microprocessor 12 checks whether the rotor 23 has been angularlydisplaced relative to the drive pinion 17 out of its basic position andthe locking element 13 has therefore taken its uncoupling position. Ifthe microprocessor 12 determines that the rotor 23 is still in its basicposition, the solenoid 11 is energized for 10 ms to 40 ms with a currentI between 0% and 10% of the maximum intensity to achieve a briefpressurization of the B pressure chambers 9 of the hydraulic workingchambers 6 with a pressure medium pressure P_(B) corresponding to thesolid-line pressure curve in FIG. 6. This is followed by a repetition ofthe releasing attempt by a renewed energization of the solenoid 11 witha current I between 90% and 100% of the maximum intensity for 40 ms to80 ms and a subsequent check by the microprocessor 12 to determinewhether the rotor 23 has left its basic position. This repetition iscarried out till the microprocessor 12 registers that the rotor 23 hasbeen angularly displaced relative to the drive pinion 17 out of itsbasic position and the locking element 13 has therefore taken itsuncoupling position. The determination of such an angular displacementof the rotor 23 out of its basic position, which can be the case alreadyafter the performance of one routine, or, as shown in FIGS. 5 and 6,only after the performance of 4 or more routines, is evaluated by themicroprocessor 12 as a successful releasing attempt, so that,immediately thereafter, the microprocessor 12 energizes the solenoid 11with a current I resulting from the operation parameters of the internalcombustion engine. This current I has an intensity situated in a rangeabove that required for the central position of the valve piston of thehydraulic valve 10 up to 100% of the maximum intensity and correspondsto an adjusted angular position of the rotor 23 relative to the drivepinion 17.

Reference numerals

1 Device

2 Cylinder head

3 Camshaft

4 Element fixed to crankshaft

5 Element fixed to camshaft

6 Hydraulic working chamber

7 Adjusting element

8 A pressure chamber

9 B pressure chamber

10 Hydraulic valve

11 Solenoid

12 Microprocessor

13 Locking element

14 Spring element

15 Reception

16 Pressure medium supply

17 Drive pinion

18 Circumferential wall

19 Side wall

20 Side wall

21 Hollow space

22 Limiting wall

23 Rotor

24 Hub

25 Vane

26 Pressure medium pump

27 Pressure medium reservoir

t Time period

P Pressure medium pressure

P_(A) Pressure medium pressure in A pressure chamber

P_(B) Pressure medium pressure in B pressure chamber

What is claimed is:
 1. A method of actuating a device for varying thevalve timing of an internal combustion engine, a camshaft adjustingdevice having a hydraulically releasable start locking, said devicegenerally comprising following features: the device (1) is arranged onthe drive-side end of a camshaft (3) mounted in the cylinder head of theinternal combustion engine and generally configured as a hydraulicadjusting drive, said device (1) comprising an element (4) fixed indriving relationship to a crankshaft of the internal combustion engineand an element (5) rotationally fixed to the camshaft (3), the element(4) fixed to the crankshaft is in power-transmitting relationship withthe element (5) fixed to the camshaft through at least one hydraulicworking chamber (6) formed within the device (1), each hydraulic workingchamber (6) of the device (1) is divided by an adjusting element (7)within the device (1) into a pressure chamber (8) and a pressure chamber(9), a pivoting or fixing of the element (5) fixed to the camshaftrelative to the element (4) fixed to the crankshaft is effected by aselective or a simultaneous pressurizing of the pressure chambers (8, 9)of each hydraulic working chamber (6), the pressurizing of pressurechambers (8, 9) of each hydraulic working chamber (6) is regulated by anelectromagnetically actuated valve piston of a hydraulic valve (10)whose solenoid (11) is actuated by a micro processor (12) as a functionof different operation parameters or the internal combustion engine, thevalve piston of the hydraulic valve (10) permits, in a non-energized orlow energized state of the solenoid (11), a pressurization of thepressure chamber (9), in a high or maximum energized state of thesolenoid (11), a pressurization of the pressure chamber (8), and in acentral position, a holding of the pressure medium pressure (P) in bothpressure chambers (8, 9) of each hydraulic working chamber (6) of thedevice (1), when the internal combustion engine has been switched offand the volume of the pressure chamber (8) of each hydraulic workingchamber (6) has been minimized, the element (5) fixed to the camshaftcan be mechanically coupled to the element (4) fixed to the crankshaftin a preferred basic position for starting the internal combustionengine, the mechanical coupling is achieved by a locking element (13)arranged on the element (5) fixed to the camshaft or on the element (4)fixed to the crankshaft, which locking element (13) can be displaced bya spring element (14) into a coupling position within a complementaryreception (15) in the element (4) fixed to the crankshaft or in theelement (5) fixed to the camshaft, the complementary reception (15) ofthe locking element (13) is hydraulically connected to the pressuremedium supply (16) to a volume-minimized pressure chamber (8) of atleast one hydraulic working chamber (6) of the device (1), uponpressurization of the volume-minimized pressure chamber (8) of eachhydraulic working chamber (6) during starting of the internal combustionengine, the reception (15) of the locking element (13) is likewisepressurized and the locking element (13) is displaced hydraulically,against the force of its spring element (14), into an uncouplingposition, characterized in that, to achieve a jam-free displacement ofthe locking element (13) into its uncoupling position, the solenoid (11)of the hydraulic valve (10) is energized during starting of the internalcombustion engine using following regulation strategy: (a) energizationfor a defined period of time (t), through a number of high frequencycycles of high and low energization (I), or through a defined number ofsuch cycles, so that the valve piston of the hydraulic valve (10)oscillates in a range about its central position and enables a rapidalternating pressurization of the pressure chambers (8, 9) of eachhydraulic working chamber (6) of the device (1) with a pressure (P) withwhich the element (5) fixed to the camshaft is held in its basicposition, (b) at the end of the defined period of time (t) or the lastcycle, the routine is broken off and followed by a renewed energizationor a holding of the high energization (I) for a further defined periodof time (t) in which the microprocessor (12) simultaneously checkswhether the element (5) fixed to the camshaft has been angularlydisplaced relative to the element (4) fixed to the crankshaft out of itsbasic position and the locking element (13) has therefore taken itsuncoupling position, (c) if the microprocessor (12) determines that theelement (5) fixed to the camshaft is still in its basic position, steps(a) and (b) are repeated till the microprocessor (12) registers that theelement (5) fixed to the camshaft has been angularly displaced relativeto the element (4) fixed to the crankshaft out of its basic position andthat the locking element (13) has therefore taken its uncouplingposition, (d) when the microprocessor (12) determines an angulardisplacement of the element (5) fixed to the camshaft out of its basicposition, energization with a current (I) defined by the microprocessor(12) which is of a higher intensity than that required for the centralposition of the valve piston of the hydraulic valve (10) and correspondsto an adjusted angular position of the element (5) fixed to the camshaftrelative to the element (4) fixed to the crankshaft.
 2. Method accordingto claim 1, characterized in that the high and the low energization (I)of the solenoid (11) of the hydraulic valve (10) is preferablycontrolled by a pulse width modulated voltage control of themicroprocessor (12), so that the energization of the solenoid (11)within one cycle is effected, once, with an electric current (I) havingan intensity between 5% above that required for the central position ofthe valve piston of the hydraulic valve (10) and 95% of the maximumintensity, and, once, with an electric current (I) having an intensityof between 5% of the maximum intensity and an intensity that is 5% lowerthan that required for the central-position of the valve piston of thehydraulic valve (10).
 3. Method according to claim 1, characterized inthat, according to a criterion for breaking off the routine defined interms of time, the duration (t) of one cycle is preferably between 4 msand 10 ms and the period of time for all the cycles required to displacethe locking element (13) into its uncoupling position till the breakingoff of the routine is preferably limited to a time (t) in the range of10 ms to 40 ms.
 4. Method according to claim 1, characterized in that,according to a numerically defined criterion for breaking off theroutine, the number of cycles required to displace the locking element(13) into its uncoupling position till the breaking off of the routineis limited to 2 to 8 repetitions.
 5. A method of actuating a device forvarying the valve timing of an internal combustion engine, particularlya camshaft adjusting device having a hydraulically releasable startlocking, said device comprising the features of the preamble of claim 1characterized in that, to achieve a jam-free displacement of the lockingelement (13) into its uncoupling position, the solenoid (11) of thehydraulic valve (10) is energized during starting of the internalcombustion engine using following strategy: a) energization with a highcurrent (I) in a defined period of time (t), so that, at first, only thevolume-minimized pressure chamber (8) of each hydraulic pressure chamber(6) of the device (1) and, thus also, the reception (15) of the lockingelement (13) is pressurized with a high pressure medium pressure(P_(A)), b) at the end of the defined period of time (t), themicroprocessor (12) checks whether the element (5) fixed to the camshafthas been angularly displaced relative to the element (4) fixed to thecrankshaft out of its basic position and that the locking element (13)has therefore taken its uncoupling position, c) it the microprocessor(12) determines that the element (5) fixed to the camshaft is still inits basic position, the solenoid (11) is energized with a low current(I) for a further period of time (t) for a brief pressurization of thepressure chamber (9) of each hydraulic working chamber (6) with apressure medium pressure (P_(B)) followed by a repetition of steps a)and b) till the microprocessor (12) registers that the element (5) fixedto the camshaft has been angularly displaced relative to the element (4)fixed to the crankshaft out of its basic position and that the lockingelement (13) has therefore taken its uncoupling position, d) afterdetermination of an angular displacement of the element (5) fixed to thecamshaft out of its basic position, energization with a current (1)defined by the microprocessor (12) which is of a higher intensity thanthat required for the central position of the valve piston of thehydraulic valve (10) and corresponds to an adjusted angular position ofthe element (5) fixed to the camshaft relative to the element (4) fixedto the crankshaft.
 6. Method according to claim 5, characterized in thatthe energization (I) of the solenoid (11) of the hydraulic valve (10) ispreferably controlled by a pulse width modulated voltage control of themicroprocessor (12), so that the solenoid (11) is energized with a highcurrent (I) of preferably between 90% and 100% and with a low current(I) of preferably between 0% and 10% of the maximum possible electriccurrent (I).
 7. Method according to claim 5, characterized in that thetime period (t) of high energization (I) is preferably between 40 ms an80 ms while the time period (t) of low energization (I) is limitedpreferably to a range from 10 ms to 40 ms.